It is commonplace in automotive vehicle instrumentation to use electric gages driving pointers mounted on the ends of gauge shafts to indicate measure of various vehicle parameters such as vehicle speed or engine RPMs. A common type of gauge has a plastic bobbin supporting an outer winding and a permanent magnet armature on a spindle within a cavity defined by the bobbin. Often a dampening fluid is placed within the cavity to prevent erratic pointer movement caused by fluctuations in the signal driving the gauge.
A characteristic of these previous types of gauges is the difficulty of creating a leak resistant seal for the cavity within which the dampening fluid and the armature are placed. A leak problem can cause a high scrap rate of gauges. Also, because the coils are crosswound on the bobbins, the flexibility of coil designs for the gauges is limited.
Another characteristic of the previous gauges is that when the armature is manufactured, often it is at first not a magnet, but a material such as a polymer bonded ferrite or any equivalent material which can be magnetized through application of a strong magnetic field to become a permanent magnet. In these cases, the magnetizing process must take place some time during the construction of the gauge. Because the magnetizing fixture cannot get close enough to the armature once the armature is inserted in the bobbin, it is difficult to magnetize the armature after insertion into the bobbin. Consequently, magnetization of the armature is usually done before insertion into the bobbin. The difficulty with this method of manufacture is that the armature is subject to attraction of dust and dirt during and after the magnetization process. These impurities are an additional contributing factor to the scrap rate of gauges.